Cellular radio communication systems typically include a number of central communication base sites. Each central communication site has a service area coverage for servicing mobile communication units within the service area. The service areas typically are arranged such that adjacent remote base site service coverage areas overlap in a manner that provides a substantially continuous service region. The substantially continuous service region provides uninterrupted service by handing off mobile communication units from one base site serving a service area to an adjacent base site serving another service area.
Pedestrian as well as mobile users will typically access the same cellular radio communication systems. For purposes of this discussion, a pedestrian user is one who roams slowly (10 kph, kilometers per hour, or less) as opposed to a mobile user (up to 100 kph or more) user. However, these cellular communication systems are typically designed to provide adequate performance for the worst case environment (i.e., the mobile user). As such, the cellular radio communication systems typically provide continual overhead measurements used by the system to maintain channel quality or perform hand-off functions. Since these measurements require the same amount of processing whether a user is a mobile user or a pedestrian user, the pedestrian user is charged the same fee for using their cellular phone as the user who is a mobile user.
Therefore, there exists a need in the industry for a personal communication system (PCS) which would provide a low tier system for pedestrian users at a reduced cost. The low tier system would provide access via radio frequency (RF) link to a basic cellular network which may or may not provide hand-off capability between low tier service areas. In addition, a high tier system should be provided for the mobile user. This high tier system would have many of the features found in current cellular systems including hand-off between high tier service areas.
In order to avoid the necessity of having two separate radio communication units to operate in the low and high tier communication system, respectively, it is desirable to provide a dual mode radio communication unit capable of operating in either the low tier or high tier communication unit. In addition, it is desirable to design the dual mode radio communication unit to utilize shared components which may be used in both low and high tier operational modes of the communication unit.